EVALUATING BEST MANAGEMENT PRACTICES IN THE SOUTH CAROLINA HORSESHOE CRAB FISHERY: A FIELD APPROACH TO DETERMINE PHYSIOLOGICAL IMPACTS OF THE BIOMEDICAL BLEEDING PROCESS

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Over 550,000 horseshoe crabs (HSCs; <i>Limulus polyphemus</i>) are harvested annually by the biomedical industry to produce Limulus Amebocyte Lysate, a medical product used to detect endotoxins in pharmaceutical drugs and medical instruments. Previous studies have found that biomedical bleeding causes sublethal behavioral and physiological effects in HSCs, and that direct morality can range from 6%-30%. The biomedical harvest is unique in South Carolina (SC) in that HSCs can be kept in holding ponds for the duration of the spawning season before the actual biomedical bleeding. In this study, a treatment consisted of bleeding animals to simulate aspects of the current SC biomedical bleeding practices. Hemolymph was sampled and hemocyanin concentration and total hemocyte counts were measured as indicators of overall health in the treatment group compared to unbled controls. Animals were held in experimental ponds for up to 8 weeks prior to bleeding to simulate local practices; mortality was low (5%) during this period. The amount of hemolymph biomedically extracted ranged from 3% to 51% (average 33%) of the total hemolymph volume of individual female HSCs. Female HSCs held in ponds for more than four weeks had lower hemocyte counts and hemocyanin concentrations prior to treatment, and those that were bled were not able to return to baseline values as quickly as control individuals. The amount of carapace epibiont coverage also impacted HSC health, with higher epibiont load negatively correlating to both physiological health metrics. There was no difference in the post-bleeding mortality rates between bled and control HSC over the course of the 12 day monitoring period (n=3 each).